Sycamore, Illinois (CNN)Charges have been dismissed against the man who spent nearly five years behind bars for the 1957 murder of a little girl in what had been touted as the nation's oldest cold case ever tried.

Jack Daniel McCullough, 76, still faces the possibility that someday a prosecutor could bring murder charges against him. But State's Attorney Richard Schmack, who believes McCullough is innocent, says he won't be filing any charges.

Asked if the murder of 7-year-old Maria Ridulph would ever be solved, Schmack said it's unlikely but noted that recent publicity about the case could rekindle somebody's memory -- or their conscience.

Both McCullough and his wife have expressed gratitude to Schmack, saying he acted with courage, and against the tide of popular opinion, during an election year. Schmack's opponent was present in court Friday just as Schmack had attended McCullough's 2012 trial when he ran for office.

With no charges hanging over him, McCullough is free to leave Illinois. He expects to begin his trip home to Seattle this weekend. He said his lawyers have advised him not to comment.

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"I'm very happy he's finally coming home. We missed him," said Sue McCullough, his wife of more than 20 years. She said his clothes will be hanging in the closet.

McCullough spoke with CNN a week ago, after Judge William Brady threw out his murder conviction and ordered him freed. But the question of whether he could be tried again had been left unresolved. And so he was back in court Friday, hoping to be cleared for good.

Prosecutor Schmack argued that the charges should be dismissed "with prejudice," meaning McCullough could never face trial again. Brady declined to go that far, saying it would require him to make a call on McCullough's guilt or innocence, which is not his role at this stage in the case.

Read the original series on the case: "Taken"

Maria Ridulph's murder went unsolved for half a century. Then detectives pursued a tip, and a man was brought to trial and convicted in the 1957 murder of the 7-year-old in Sycamore, Illinois. Now that man is free. Ann O'Neill's 2013 series on the case, "Taken," raised questions about whether the trial was unfairly one-sided.

Instead, Brady dismissed the murder charge, leaving the door open for new charges and another trial someday.

"I've only been doing this for 41 years, and I have never signed an order for dismissal with prejudice," Brady said. He did dismiss a kidnapping charge against McCullough for good, though, because an appeals court had already reversed that conviction based on the statute of limitations.

Brady postponed ruling on a request by the victim's brother to appoint a special prosecutor. Hundreds of Sycamore residents signed a petition backing the request, including Sycamore Mayor Ken Mundy.

Charles Ridulph, a 70-year-old church deacon, is certain McCullough killed his 7-year-old sister, Maria, and is looking to keep this cold case closed. The petition, which was circulating around town and on social media, urged residents of "old Sycamore" to "stand up" with Ridulph.

"We have lost all confidence in the impartiality and integrity of our criminal justice system," the petition states, leveling sharp criticism at Schmack.

Jack McCullough walks out of the DeKalb County Courthouse in Sycamore, Illinois, with Crystal Harrolle, an investigator with the public defender's office.

More than 200 people had signed by the time the petition was filed with the court on Thursday afternoon. By Friday morning, the number had doubled.

"It was everywhere," said Mundy, whose name topped the list of signatures. He also filed a personal letter with the court, saying that a special prosecutor would restore the community's faith in the justice system.

Mundy, a longtime friend of the Ridulph family, called Schmack a "rogue" prosecutor "who refused to follow the law" and respect the decisions of the trial and appeals courts.

In delaying a decision on the request for a special prosecutor until a June 23 hearing, Brady said, "I am not blind to the fact that there are many people who would want to see this case resolved through a trial. It doesn't surprise me." But then he questioned whether he was being called on to deliver justice in a court of public opinion. "Is whoever brings the most petitions how I decide the case?" Brady asked.

After Friday's hearing, Ridulph spoke to reporters on the courthouse steps.

"The people of Sycamore have been so supportive from the beginning," he said, his voice catching slightly. "Their support and the hundreds of signatures joining my petition -- collected over a matter of hours, mere hours -- speaks of the love in the community of Sycamore."

Shadow over Sycamore

A plaque remembering Maria Ridulph stands in front of Sycamore's police station, and the mystery of what happened to her has cast a long shadow for more than half a century.

Sycamore has grown since 1957 from an isolated farming town of 7,000 to a Chicago exurb of 17,600 people. But nearly everybody knows about Maria, the little girl who was snatched away by a man who called himself "Johnny" and gave her a piggyback ride on a snowy December evening.

McCullough grew up in a tiny, crowded house around the corner from the Ridulphs and joined the U.S. Air Force less than two weeks after the girl vanished.

The FBI questioned and cleared him before he left home, but he was arrested in Seattle in 2011 after investigators began looking into the case again following a tip from a half-sister. McCullough was taken to Sycamore and tried the following year by a judge brought in from a neighboring county.

Jack McCullough, in prison after his 2012 conviction. Now a judge has dismissed all charges against him.

Although the case spanned 55 years by then, testimony lasted just four days. Among the witnesses against McCullough were several of his siblings. People who crowded into the courtroom cheered when the guilty verdict was announced.

McCullough always insisted he was innocent -- and always said he could prove it. That proof was contained in the thousands of pages of police and FBI reports that were barred from his trial, he said.

Schmack agreed and dropped a bombshell on Sycamore in late March. He filed court papers stating that McCullough is innocent and sought his immediate release from prison. The prosecutor said he spent about six months reviewing the files his predecessor, Clay Campbell, had left behind.

Schmack concluded that prosecutors and state police made two key missteps: They tweaked the timeline, moving up the time of the abduction to fit their theory for the crime, and they ignored details that didn't support that theory.

Schmack found no evidence that Maria could have been missing "a little after 6," as Illinois State Police investigators had theorized. Instead, he concluded, the FBI got it right in 1957: Maria more likely vanished between 6:45 and 7 p.m.

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Among the evidence the prosecutor reviewed was CNN's 2013 series on the case, "Taken," which examined McCullough's murder trial and raised questions about whether it was fair. CNN was able to review some, but not all, of the FBI reports for the series after requesting them from the National Archives. The U.S. Justice Department declined a request to review all the reports at the time, stating that the Ridulph case remained under investigation.

Schmack inherited the case from Campbell, whom he narrowly defeated in an election a few weeks after the guilty verdict. Schmack sat through the trial, which Campbell prosecuted personally, and said he always considered the evidence thin. When McCullough persisted in filing appeals, Schmack decided he'd better learn more about a case he might be called on to defend.

Instead, he said, the evidence led him to an inescapable conclusion: McCullough is innocent.

In his filings with the court, Schmack said he was ethically bound to right a wrongful conviction. And he minced no words in a scathing assessment of the case that others had built against McCullough.

Prosecutor Richard Schmack reviewed the case and asked for McCullough to go free.

He went so far as to allege that "fraudulent" evidence and "false" testimony were used to obtain warrants and grand jury indictments.

In pressing for dismissal with prejudice, Schmack cited an appeals court's findings that the FBI and police reports from 1957 could have come into the trial. He said he disagreed with the appeals court's ruling that barring the records was a "harmless error." Not allowing the records into evidence unfairly prevented McCullough from establishing his alibi, Schmack concluded.

"The demonstrated pattern of clearly inaccurate testimony, intended or otherwise, and misleading presentations to two grand juries and two judges in two states all shielded by an erroneous ruling which buried any effective impeachment at trial borders on remarkable," he stated in his report.

Once all the evidence -- including the police reports -- is presented at a new trial, Schmack concluded, "there is insufficient evidence to support the judgment of guilt in this case."

Friday's hearing may not be McCullough's last appearance in a Sycamore courtroom. He has indicated he plans to sue the state of Illinois over his wrongful conviction.